Although normally an AI needs a high-end computer core memory to reside in, the MJOLNIR Mark V armor system is equipped with a revolutionary crystal memory system that makes Cortana portable. Due to her extensive experience at infiltrating enemy systems and access to Naval Intelligence hacking routines, Cortana is also able to transfer from system to system even without the use of a hard-coded key like the one used by Captain Jacob Keyes. Contrary to some observations, Cortana does not reside on the "key card" that Captain Keyes transfers form the Pillar of Autumn's computer to the MJOLNIR suit -- this is merely the authorization key needed for Cortana to make the transfer from the ship's core memory to the memory matrix in the MJOLNIR suit. The need for a coded physical key is supposed to prevent AI from moving from system to system at will. Though Cortana is among the few AI who can get around this limitation with effort, it's a classified ability and she does not flaunt it.

There was a little confusion over its authenticity, but Brannon Boren himself, being the good sport he is, wasted little time in confirming his part in it. However, according to Brannon, he added this under the assumption that it was already in one of the books, which it is unfortunately not. So, as this clearly stems from his first hand knowledge of the source material, it was correct, though it may not be any more ;)

Thank Brannon; fascinating. It's stuff like that that makes our day :)